Refinement of TSLP expression mediates chronic allodynia associated with IL22/STAT3 axis

Abstract

Chronic allodynia is a painful response to an innocuous stimulus because of maladaptive neuroplasticity within the central nervous system. IL22 is a pleiotropic mediator owing to its proinflammatory and immunosuppressive effects. In this study, we aimed to investigate the potential of modulating TSLP expressions to treat chronic allodynia and elucidate the underlying mechanisms associated with IL22. TSLP^−/− mice were generated, and four mouse groups were created as follows: wild-type (WT) + PBS, TSLP knockout (KO) + PBS, WT + bleomycin, and TSLP KO + bleomycin. Repeated bleomycin administration reduced the IL22/STAT3 pathway to trigger chronic allodynia in C57BL/6 mice. The degree of gliosis and neuron loss were significantly greater in the somatosensory cortex and spinal cord dorsal horn of the bleomycin-treated mice compared with those in the PBS-treated mice. Compared with those in WT mice treated with bleomycin, in TSLP-deficient mice, the degree of gliosis and neuron loss were significantly lower in the somatosensory cortex and spinal cord dorsal horn and the mechanical withdrawal threshold was altered. Differentiated human SH-SY5Y cells were created to investigate the neuroprotective effects of TSLP refinement against hydrogen peroxide (H₂O₂)-induced neurotoxicity. The deficiency of TSLP protected differentiated SH-SY5Y cells against H₂O₂-induced neurotoxicity. IL22 stimulator not only rescued the H₂O₂-induced neurotoxicity but augmented the protective effect of si-TSLP on differentiated SH-SY5Y cells. Our data confirmed that a lack of TSLP decreased the expression of TSLPR/STAT5, the bleomycin-induced chronic allodynia and the H₂O₂-induced neurotoxicity. In addition, inhibiting TSLP rescued the IL22/STAT3-mediated effect, which regulated neuroglial interactions to relieve chronic allodynia. Targeting TSLP/TSLPR is a potential therapeutic approach for relieving chronic allodynia by regulating gliosis, neuron loss, and the IL22/STAT3 axis.